1. Field of Invention
The present invention relates to a safety device for preventing a worker from mistakenly operating an overlock sewing machine.
2. Description of the Conventional Art
In known overlock sewing machines, a cross-stitch S1 (as shown in FIG. 3) or a covering stitch S2 (as shown in FIG. 4) is selected according to the operation which is desired.
The conventional overlock sewing machine M of this type is illustrated in FIGS. 5 to 7.
A main body M1 of the overlock sewing machine, as well known, contains a lower looper Ld and an upper looper Lu, which cooperates with a needle N to form a stitch, a control mechanism for controlling the device of those loopers and the needle, a motor serving as a drive source, and the like.
A main body M1 of the overlock sewing machine is contoured by a main body cover 1, a looper cover 2, a cloth table 3, and the like. A cloth waste cover 4 (FIG. 5) or an auxiliary cloth table 5 (FIG. 6) is selectively set to the looper cover 2 and the cloth table 3 in accordance with the type of stitch to be formed. Specifically, to form the cross-stitch S1 (FIG. 3), the cloth waste cover 4 is set to the looper cover. To form the covering stitch S2 (FIG. 4), the auxiliary cloth table 5 is set to the looper cover.
To form the cross-stitch S1, it is necessary to operate the needle N, the upper looper Lu, and the lower looper Ld. To form the covering stitch S2, it is necessary to operate the needle N and the lower looper Ld. A selector D is provided to operate the sewing machine in accordance with the type of the stitch (the cross-stitch S1 or the covering stitch S2). To form the cross-stitch S1, the selector D is turned to a position S1 and the cloth waste cover 4 is set to the looper cover 2 as shown in FIG. 5. To form the covering stitch S2, the selector D is turned to a position S2, and the auxiliary cloth table 5 is set to the looper cover 2 as shown in FIG. 6. An auxiliary head plate 5a is fastened to the top surface 5b of the auxiliary cloth table 5. The auxiliary head plate 5a is flush with a needle plate NB. With this, space of a stitching stage can be effectively used. Accordingly, it is possible to stitch a large cloth.
The looper cover 2 may be swung about an axis x between a stand-up position and a laid-flat position (FIG. 7). Usually, the looper cover 2 is urged in the direction that is opposite to the direction of an arrow in FIG. 7. When urged in that opposite direction, the looper cover 2 is prohibited from being swung. When moved in the direction of the arrow, it is allowed to be turned.
To operate the sewing machine, a worker sets the selector D to the position S1 or S2, sets the cloth waste cover 4 or the auxiliary cloth table 5 to the looper cover 2 in accordance with the selected position, and then closes the looper cover 2. Then, he starts the operation of the stitching operation.
In handling the overlock sewing machine, to change the cross-stitch S1 to the covering stitch S2, the worker operates the selector D for the stitch type change, and exchanges the cloth waster cover 4 with the auxiliary cloth table 5. However, an unskilled worker frequently starts the operation of the sewing machine while missing one of these procedural steps of operation. In this case, the sewing machine will form a stitch different from the desired one. In an extreme case, the machine will be broken.
For example, when the cross-stitch forming operation starts in a state that the auxiliary cloth table 5 is set to the looper cover, the upper looper Lu, which is vertically moving, hits the auxiliary cloth table 5. As a result, the upper looper Lu and/or the auxiliary cloth table 5 will be damaged or broken. Sometimes, broken pieces are scattered and injure hurt the worker.